The invention relates to the field of collision shock absorbing systems and more particularly to a modular, two-stage, energy-absorbing system for improving the energymanagement effectiveness of the primary crush zone of a vehicle at speeds of from 5mph to about 30+mph for both direct and oblique collisions.
Those skilled in the art are aware of the problem that occupants of small cars involved in accidents suffer 30 to 40% higher injury and death rates compared to occupants in larger cars that weigh from 1,000 to 1,500 lbs more. This dangerous and costly reality will be aggravated as the auto industry seeks answers to long-term energy problems by emphasizing the small car in America over the next 10 to 20 years. The safety and security a large car offers to the buyer is not only psychological but is based on fact. A study of 23,000 highway accidents submitted during the July 1974 International Congress on automotive safety revealed an inverse relationship between car size and occupant injuries. In many types of accidents, injuries in smaller cars were double in number of those in fullsize cars.
The statistical evidence is further substantiated by a series of high-speed test crashes between large and small cars. Consumer buying habits reflect a number of considerations among which is found to be the crashworthiness of a vehicle as a predominate concern to the car owner. Repairs and insurance premiums are obviously also found to be costs of major concern. Thus crashworthiness is one important reason why the majority of car owners have always striven to own as large a car as possible.
Approximately one-fourth of American automobiles and over 30 million Americans are involved in auto accidents each year. More than 70% of U.S. auto accident injuries involve occupants. Over 80% of occupant injuries occur at impact speeds (Barrier Equivalent Velocity: BEV) below 40mph. More than 75% of accidents involve front and rear ends and corners of automobiles. Thirty-six percent of reported injuries and 60% of fatalities are above 30mph (BEV). Serious and fatal injuries on the average are 100% more frequent in small cars weighing under 2,900 lbs. This applies to both belted and unbelted occupants. Injuries in small cars striking each other average 75% more than in large cars striking each other. Crash data indicate that automobile weight differences alone have little net effect on overall injury rates. Airbag deployment problems are inherent in small cars. Crash data and tests indicate that small car injuries are aggravated by the automobile's short body crush deceleration distances which is the basic safety deficiency of the small car.
The automotive industry and research firms have devoted much time to reinforcing small cars to maintain passenger compartment structural integrity without changing the car body crush deceleration distance in frontal collisions. These experiments merely add weight to the vehicle while simultaneously imposing intolerably high "G" loads on the occupant (as shown by instrumented dummies in tests) as a result of strengthening the vehicle without adding more deceleration distance.
Tests conducted by the auto industry and the government show specifically how crush distance is a major factor in providing a ride down or deceleration distance for the occupant. In cases where occupants are using a belt, harness or airbag system the reduction in bodily injury in frontal collisions becomes directly proportional to the vehicle deceleration distance and its effectiveness in managing the collision energy over as long a stroke as possible through the vehicle body's primary and secondary crush zones. Accordingly, the effectiveness of any occupant interior restraint system is in direct proportion to the vehicle's crashworthiness and the ability of its exterior body to absorb collision energy. In small cars, the exterior body does not have sufficient energy absorbing capacity. The only way this basic safety deficiency can be solved without gas mileage penalties is to restore body crush distance with a light weight, energy management system. Over 50% of reported accidents involve the front and rear ends and corners of the vehicle and are above 10mph BEV. Forty percent are from 10 to 20mph. The average repair costs in a 15mph accident are now $1200 and rising. In many accidents, when the car is hit at 10 to 15mph in the corner at fender level, the fender will buckle well behind the impact area because the corner is stronger than the area behind thereby causing extensive damage. A stock fender being a one piece panel and not flexible thus aggravates the car's overall damageability factor.
In addition to these principal problems, there are other considerations. Energy conservation will require lighter weight and more efficient automobiles. The currently accepted methods of reducing weight in mass produced conventional vehicles will result in smaller cars with reduced effective body crush distances. The costs of collision repairs and bodily injuries are rising at a rate which is increasing insurance premiums to an impractical level without offering economical relief to the insurance industry or to the car owner. It has been stated that the "adverse problems" of solving vehicle crashworthiness and gas mileage efficiency were "extremely complex" and would require many years of research and many billions of dollars. Furthermore, existing government reports state that further advanced concepts for reducing collision repair costs above 10 are not available for evaluation. Federal laws call for a substantial decrease in collision repair costs and also give the Secretary of Transportation the authority to prevent cars from being delivered to the consuming public when they are deemed to have a basic safety deficiency. To date no solutions have been proposed to simultaneously reduce collision repair costs substantially while improving the crashworthiness of the vehicle and do so without affecting the gas mileage or mass production system for the economy car. The basic safety deficiency of small cars is now being aggravated in more types of vehicles including full size cars as front ends are shortened in attempts to save weight. This conventional approach also allows most collisions to penetrate into the expensive part of the vehicle.
Recent government tests dramatically show the basic safety deficiencies of the stock small economy car, particularly when colliding it with a full size car in simulated highway frontal collisions at speeds equivalent to 40 mph barrier equivalent velocity (BEV). After the collisions, the small cars had no room left for the driver. The instrumented dummy clearly indicated that at best any occupant restraint system would merely have turned a quick fatality into a permanent cripple. In collisions of small cars equipped with airbags, the bag does not fully deploy until 30 to 40% of the vehicle's already deficient crush distance is destroyed. The small stock car can be equipped with expensive radar sensing equipment to deploy the airbag early, but the cost of this type of system and other related factors is great. A passive restraint system still cannot provide the crashworthiness of the body crush distance found in larger cars.
The technology proposed by those skilled in the art (soft faces and five mph safety bumpers, etc.) cannot keep pace with the rising cost of collision repairs or reduce repair costs in ten to twenty mph collisions particularly at frontal angles. Current and planned mass produced economy cars, using the latest in materials and processing methods, have been declared by many experts as being incompatible with further improvements in vehicle crashworthiness. The proliferation of aggressive conventional bumper devices used to meet bumper standards have precluded the possibilities of overall solutions to crashworthiness and damageability from being developed and introduced into the market place.
The current problem facing the automotive industry is that even though bigger is safer, how can the consumer continue to be sold larger, prestigious looking automobiles, when gasoline mileage legislation and resource conservation are becoming critical problems. Furthermore, nothing of major importance in reducing accident damage costs and repair time is forthcoming. The direction of the industry has been further confirmed by statements to the effect that "we have reached the end of our safety technology", and "to expect improved collision damage protection at 15mph would be completely unreasonable," etc. are examples of recent testimony in Washington, D.C. opposed even to a continuance of 5mph bumper standards.
Among the prior art items to be considered are U.S. Pat. Nos. 3,702,711; 3,802,727; 3,721,433; 3,784,182; 3,610,609; 3,638,985; 3,794,342; 2,829,915; 3,224,924; 3,836,192; 3,224,924; 3,744,835; 3,888,502; 3,797,873; Great Brit. Pat. No. 1 068 434; Deutsches Auslegeschrift 1 923 305 (1970); and a paper entitled "Necessary Considerations in the Design, Analysis and Performance Assessment of Crashworthy Structures and Protective Systems" published in a book entitled "Measurement and Prediction of Structural and Biodynamic Crash-Impact Response" by the American Society of Mechanical Engineers, 1976.